Method for detecting cancer using icg fluorescence method

ABSTRACT

A method of detecting an accessory cancer lesion, comprising an administration step wherein indocyanine green is administered to a living body, an irradiation step wherein a target organ suspected of having cancer is surgically exposed and irradiated with excitation light of indocyanine green, an imaging step wherein a near-infrared fluorescence intensity distribution image from the excited indocyanine green in the target organ is obtained, and an identification step wherein an area having the near-infrared fluorescence in the intensity distribution image, excluding the area detected in preoperative examination or intraoperative macroscopic observation, is identified as an accessory cancer lesion.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of detecting cancer using anICG fluorescence method. The present invention further relates to amethod of detecting an accessory cancer lesion and a device usedthereof, a method of treating the cancer, and an accessory cancer lesiondetection agent and composition thereof.

2. Related Background Art

Computer tomography (CT), nuclear magnetic resonance imaging (MRI), andultrasonographic imaging are widely used as methods of imaging a cancerlesion. For example, contrast CT, wherein an iodinated contrast agenthaving high x-ray absorption is injected into a blood vessel (normally aperipheral vein), is generally used for testing cancer by CT (see, forexample, National Publication of International Patent Application No2007-533737).

SUMMARY OF THE INVENTION

However, even when the cancer lesion is identified by a method describedabove, or any other known imaging method, and resected, this does notlead to complete cure of the cancer in many cases.

For example, the 5-year recurrence-free survival of patients who haveundergone radical resection of hepatocellular carcinoma (HCC) is as lowas about 30%. One suspected reason for this low survival, especially incases of early recurrence that occurs within 2 years post surgery isthat the accessory cancer lesion that cannot be detected by conventionalpreoperative examination or intraoperative macroscopic observation ismissed in the resection. Thus, there is a need to improve thesensitivity of detecting the accessory lesion before and during thesurgery, in order to completely cure the cancer.

The object of the present invention is therefore to provide a detectionmethod that enables the detection of an accessory cancer lesion.

The present invention provides a method of detecting an accessory cancerlesion, comprising an administration step wherein indocyanine green(ICG) is administered to a living body, an irradiation step wherein atarget organ suspected of having cancer is surgically exposed andirradiated with indocyanine green excitation light, an imaging stepwherein a near-infrared fluorescence intensity distribution image fromthe excited indocyanine green in the target organ is obtained, and anidentification step wherein an area having the near-infraredfluorescence in the intensity distribution image, excluding the areadetected in preoperative examination or intraoperative macroscopicobservation, is identified as an accessory cancer lesion.

By employing this method, an accessory cancer lesion can be detectedintraoperatively in an area where it has not been detected by x-ray(CT), MRI, ultrasonography, or macroscopic observation of the targetorgan. Therefore, the method can prevent the missing of a minuteaccessory cancer lesion during surgery, and improve postoperativesurvival. In the present invention, the lesion detected by preoperativeexamination (x-ray, MRI, ultrasonography, etc) or through intraoperativemacroscopic observation is termed “main cancer lesion”.

A conventional test for liver function is performed wherein indocyaninegreen (a dye) is injected into a vein in the arm, blood is collectedafter the lapse of a certain time, the residual dye in the blood isquantitatively determined, and the amount of dye processed by the liveris calculated. However, the present inventors were the first to discoverthe phenomenon of intravenously injected indocyanine green that isneither complexed with a high density lipoprotein nor has antibodiesagainst proteins specifically present in cancer tissue, accumulating todetectable levels not only in the main lesion but also in the accessorylesion.

The application of the above-described method provides an excellentmethod of treating cancer. In short, a method of treating cancer byshrinking, destroying or resecting an area containing at least oneaccessory lesion identified by the method of detecting an accessorycancer lesion can be provided.

It became clear from the above finding that the indocyanine greenfunctions as a detection agent for an accessory cancer lesion. In otherwords, the indocyanine green that is neither complexed with a highdensity lipoprotein nor bound to antibodies against proteinsspecifically present in an accessory lesion effectively functions as anaccessory cancer lesion detection agent.

The indocyanine green need not be used alone; it can be used in the formof a distilled water-containing composition, for detecting an accessorycancer lesion.

In other words, the use of the indocyanine green, or a compositioncontaining indocyanine green and distilled water, for detecting anaccessory cancer lesion is provided.

Further, the present invention provides a data collection methodcomprising comparing a near-infrared fluorescence intensity distributionimage obtained by irradiating the target organ in a living body intowhich indocyanine green has been administered with indocyanine greenexcitation light, with a cancer lesion distribution image obtained bythe use of x-rays, nuclear magnetic resonance or ultrasound on thetarget organ before administering the indocyanine green, and collectingthe data of an area that is detected in the near-infrared fluorescenceintensity distribution image but not in the cancer lesion distributionimage as accessory cancer lesion area data.

According to this method, the data on the accessory cancer lesion(including boundary information, such as location, size, etc, of theaccessory cancer lesion) can be collected from an area of the targetorgan that are not detected by x-ray CT, MRI, ultrasonography, ormacroscopic observation. In other words, the data collection method ofthe present invention is a method of collecting data on a human body forassisting the final diagnosis. The use of such data can prevent themissing of a minute accessory cancer lesion by doctors, and improve thepostoperative survival of the patient. In the present invention, alesion detected in the cancer lesion distribution images obtained by theuse of x-rays, MRI, or ultrasound on the target organ beforeadministering the indocyanine green is termed “main cancer lesion”.

It is preferable to obtain the near-infrared fluorescence intensitydistribution image of the target organ after intravenous injection ofindocyanine green, and it is preferable to obtain the intensitydistribution image of the target organ 1 to 10 days after indocyaninegreen administration.

Furthermore, it is preferable to obtain the near-infrared fluorescenceintensity distribution image of the target organ in a living bodyadministered with indocyanine green that is neither complexed with ahigh density lipoprotein nor bound to antibodies against proteinsspecifically present in an accessory cancer lesion. However, thenear-infrared fluorescence intensity distribution image can also beobtained from a target organ in a living body to which indocyanine greenin the form of the above-described complex, or indocyanine green boundto the above-described antibodies, has been administered.

The device described below can be used in the above-described accessorycancer lesion detection method and data collection method. In otherwords, one can use an accessory cancer lesion detector, which detects anaccessory cancer lesion during the surgery for shrinking, destruction,or resection of a cancer lesion, and comprises an irradiation means forirradiating the target organ suspected of having cancer in a living bodyinto which indocyanine green has been administered with indocyaninegreen excitation light, and an imaging means for obtaining thenear-infrared fluorescence intensity distribution image from the excitedindocyanine green in the target organ.

In this device, it is preferable that the irradiation means and imagingmeans are installed in an integrated manner so that the device can bebrought close to the site of the accessory lesion exposed by thesurgery. This type of configuration enables image acquisition, forinstance, by bringing the device close to the cancer lesion after theabdomen has been surgically opened.

Effect of the Invention

The present invention can provide a method of detection that enables thedetection of an accessory cancer lesion and a data collection method foran accessory cancer lesion area, and therefore, can improve the 5-yearrecurrence-free survival of patients who undergo radical cancer surgery.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a configuration diagram of an embodiment of the accessorycancer lesion detector;

FIG. 2 is a perspective view showing the configuration of the excitationlight source unit and imager used in the detector shown in FIG. 1;

FIG. 3 shows images of a cancer lesion obtained by contrast CT and theICG fluorescence method, and micrographs of a cancer lesion; 3A is animage obtained by contrast CT, 3B is a near-infrared fluorescenceintensity distribution image from ICG in the liver, 3C is a micrographof a tissue section of an accessory lesion, and 3D is a magnified imageof the micrograph of 3C;

FIG. 4 shows images of a cancer lesion obtained by contrast CT and theICG fluorescence method, and micrographs of a cancer lesion; 4A is animage obtained by contrast CT, 4B is a near-infrared fluorescenceintensity distribution image from ICG in the liver, 4C is a micrographof a tissue section of an accessory lesion, and 4D is a magnified imageof the micrograph of 4C;

FIG. 5 shows images of a cancer lesion obtained by contrast CT and theICG fluorescence method, and micrographs of a cancer lesion; 5A is animage obtained by contrast CT, 5B and 5C are near-infrared fluorescenceintensity distribution images from ICG in the liver, and 5D is amicrograph of a tissue section of an accessory lesion;

FIG. 6 shows images of a cancer lesion obtained by contrast CT and theICG fluorescence method, photographs of a resected cancer lesion, andmicrographs of a cancer lesion; 6A is an image obtained by contrast CT,6B is a near-infrared fluorescence intensity distribution image from ICGin the liver, 6C and 6G are photographs of formalin-fixed liver, 6D and6H are near-infrared fluorescence intensity distribution images from ICGin the resected liver (they respectively correspond to 6C and 6G), and6E, 6F, 6I, and 6J are micrographs of lesion tissue (6F is a magnifiedimage of 6E and 6J is a magnified image of 6I); and

FIG. 7 shows images of a cancer lesion obtained by contrast CT and theICG fluorescence method, and micrographs of the cancer lesion; 7A is animage obtained by contrast CT, 7B is a near-infrared fluorescenceintensity distribution image from ICG in the liver, 7C is a micrographof a tissue section of an accessory lesion, and 7D is a magnified imageof the micrograph of 7C.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A preferred embodiment is described below, referring to the drawings. Inthe description of the drawings, identical symbols are assigned to thesame components, and duplication of descriptions is avoided.Furthermore, parts of the drawings are exaggerated to facilitate betterunderstanding, and the dimensional proportions do not always match withthose of the components described.

First, the method of detecting an accessory cancer lesion will bedescribed. The method of detecting an accessory cancer lesion of thepresent invention comprises the above-described administration step,irradiation step, imaging step, and identification step. Now a preferredembodiment is described stepwise.

In the administration step, indocyanine green is administered to aliving body (human or non-human mammal). In this step, normally, theindocyanine green is administered through intravenous injection, and itis preferable for the indocyanine green used in this step to be neithercomplexed with a high density lipoprotein nor bound to antibodiesagainst proteins specifically present in an accessory cancer lesion.Further, it is preferable to intravenously inject the indocyanine greenalong with distilled water, in the form of a composition for detectingan accessory cancer lesion. The content of indocyanine green in theaccessory cancer lesion detecting composition can be suitably decided,taking into account the type and stage of the cancer, and the age andbody weight of patient (or animal patient). It is preferable to carryout this step before starting the surgery for shrinking, destruction, orresection of the cancer.

Next, the irradiation step, wherein indocyanine green excitation lightis irradiated on the target organ suspected of having the cancer, iscarried out. Near-infrared light (700 to 1000 nm, particularly 700 to800 nm) is preferable as the excitation light. The use of a lightemitting diode (LED) or a semiconductor laser (LD) is preferable as thespecific means in the irradiation step. Alternatively, one may use anoptical filter (such as a low pass filter that allows the passage oflight of wavelength 800 nm or less, or a band pass filter with a centerwavelength of 760 nm) fitted to a halogen lamp of about 150 W as theexcitation light source, and light from this source may be irradiatedthrough optical fibers. The intensity of the excitation light and theexcitation time can be decided suitably, depending on the amount ofindocyanine green introduced, the size of the cancer lesion, etc. Thisstep is preferably carried out after the start of the surgery forshrinking, destruction, or resection of the cancer lesion but beforecarrying out the shrinking, destruction or resection.

Next, the near-infrared fluorescence intensity distribution image fromthe excited indocyanine green in the target organ is obtained in theimaging step.

The near-infrared fluorescence from the excited indocyanine greentypically has a wavelength of 800 to 900 nm (825 to 850 nm inparticular). Therefore, the near-infrared fluorescence intensitydistribution image is obtained using an imaging means that can capturelight of the concerned wavelengths. Examples of such imaging meansinclude solid state imagers such as CCD cameras. When using a CCDcamera, it is preferable to remove the infrared cut filter.

The imaging step is preferably carried out 1 to 10 days, more preferably3 to 5 days, after the indocyanine green administration step. If theimaging is done soon after the administration of the indocyanine green(in less than 1 day from the administration step), sometimes,near-infrared fluorescence is obtained from all parts of the targetorgan, and there is the possibility of not being able to differentiatethe lesion from normal tissue. Beyond 10 days after the administrationstep, the near-infrared fluorescence sometimes becomes faint even in thelesion.

The present inventors do not wish to adhere to one particular theory,but assume that the indocyanine green gets accumulated in theneovascularized part of the cancer lesion. New blood vessels arecontinuously formed one after the other in a cancer lesion. It isconceivable that the indocyanine green can easily leak out from thenewly formed blood vessels, and therefore, it gets accumulated aroundthe newly formed vessels.

The imaging step is preferably carried out after the start of thesurgery for shrinking, destruction, or resection of the cancer lesionbut before carrying out the shrinking, destruction or resection. Inother words, it is preferable to do the imaging after starting thesurgery for treating the cancer, but before actually treating the cancerlesion. As for the surgical method, resection is considered to be mostsuited for the method of the present invention.

It is suitable to do the imaging 2-dimensionally or 3-dimensionally allover the target organ. In this manner, the location of the cancer lesion(a main lesion and/or an accessory lesion) that are the targets ofshrinking, destruction or resection can be accurately identified.

Next, the identification step is carried out. In this step, the areahaving near-infrared fluorescence, other than the area of the intensitydistribution image already detected in the preoperative examination orintraoperative macroscopic observation is identified as the accessorycancer lesion.

In the identification step, the area, other than the area (main lesion)detected by x-ray CT, MRI, ultrasonography, or macroscopic observationof the target organ, can be identified as the accessory lesion. In thiscase, there may be more than one accessory lesion identified.

The cancer targeted by the present invention is preferably a solidcancer (primary cancer) such as gastric cancer, esophageal cancer, coloncancer, liver cancer, etc, but it can be metastatic cancers that havemetastasized from a cancer of some other organ. Among the solid cancers,liver cancer, hepatocellular carcinoma in particular, is suitable forapplying the method of the present invention because patients of suchcancers have low postoperative survival. Furthermore, the subject(living body) to be tested can be a human or non-human mammal.

A novel method of treating cancer, where the accessory cancer lesiondetection method of the present invention is used, is provided. In otherwords, a method of treating cancer is provided, wherein the area havingat least one accessory lesion identified by the accessory cancer lesiondetection method is shrunk, destroyed, or resected. In this treatmentmethod, usually, the main cancer lesion is shrunk, destroyed or resectedalong with the area having at least one accessory lesion.

As described above, the indocyanine green functions as the accessorycancer lesion detection agent. In other words, the indocyanine greenfunctions as a detection agent that detects an accessory lesion presentin an area where no lesion is detected in the x-ray imaging, MRI,ultrasonography, or macroscopic observation. As described for theadministration step, indocyanine green that is neither complexed with ahigh density lipoprotein nor bound to antibodies against proteinsspecifically present in the accessory lesion is suitable.

The accessory cancer lesion detection agent is effective for livercancer, especially hepatocellular carcinoma. It is preferable toadminister it to the living body (human or non-human mammal) at such atime that the detection would be done 1 to 10 days later.

Next, the data collection method of the present invention is described.In the data collection method of the present invention, thenear-infrared fluorescence intensity distribution image is obtained byirradiating the target organ in the living body into which indocyaninegreen has been administered with indocyanine green excitation light.Besides this, a cancer lesion distribution image of the target organ isobtained by the use of x-rays, nuclear magnetic resonance or ultrasound,before administration of the indocyanine green.

The near-infrared fluorescence intensity distribution image from thetarget organ of a living body to which indocyanine green has beenadministered can be obtained in above-described mode.

The cancer lesion distribution image is obtained by the use of x-rays,nuclear magnetic resonance or ultrasound to the target organ before theindocyanine green administration. The lesion detected by such imaging isthe main cancer lesion, and the detectable size of such lesion is about5 mm in the long axis direction.

The cancer lesion distribution image obtained by the use of x-rays,i.e., the x-ray image (CT), can be captured using, for instance, theAquilion 16 (trademark) medical x-ray CT system (manufactured by ToshibaMedical Systems Corporation) or similar equipment. The nonlimitingexemplified condition for capturing x-ray image (CT) of a liver is: tubevoltage 120 kV, tube current 400 mA, rotation time 0.5 sec/rotation,pitch 1.5, and slice thickness 1 mm. Examples of iodinated contrastagents include Iopamiron (registered trademark) (Bayer HealthCare),which has iopamidol (generic name) as the active ingredient. Forinstance, 370 mg (95 mL) of Iopamiron may be injected at the rate of 4mL/sec. A scan delay time of 20 sec may be used in case of earlyarterial phase (screening), about 30 sec for late arterial phase(detailed examination), and about 80 sec for portal venous phase(detailed examination) scanning. The dose of the x-ray is to be setaccording to the size of a patient.

The cancer lesion distribution image obtained by the use of nuclearmagnetic resonance, i.e., the nuclear magnetic resonance image (MRI),can be captured by using, for instance, the MAGNETOM Symphony 1.5T(manufactured by Siemens AG) MRI system or similar equipment. Theprocedure for capturing image is not specifically restricted andexemplified by the following method. Firstly, before injection of thecontrast agent, slice images along the three axis directions, i.e.,coronal, sagittal, and transverse, are acquired under the staticcondition. Next, the contrast agent is injected, and dynamic imaging iscarried out. More specifically, after deciding the imaging site, a bolusof the contrast agent is injected intravenously, and the changes withtime in the three axis directions are captured at intervals of about 10sec. In some cases the imaging may done along one axis direction only.Finally, after the lapse of sufficient time from the injection of thecontrast agent, slice images along the three axis directions arecaptured as static contrast-enhanced images. Among these nuclearmagnetic resonance images, the dynamic images are particularly effectivefor assessing the quality of a cancer lesion.

The cancer lesion distribution image obtained by the use of ultrasound,i.e., the ultrasound image, can be captured, for instance, using thedigital diagnostic ultrasound system EUB-8500 (manufactured by HitachiMedical Corporation) or similar equipment. The imaging frame rate andpower level can be set by a person skilled in the art, based on thelocation, size, etc of the target organ.

Data on the accessory cancer lesion area is then collected from the twotypes of images obtained by the methods described above. In other words,data on the area detected by the near-infrared fluorescence intensitydistribution image, but not detected in the cancer lesion distributionimage is collected as the data on the accessory cancer lesion area.

The accessory cancer lesion area data can be identified by superimposingthe near-infrared fluorescence intensity distribution image and thecancer lesion distribution image. Such superimposition can be donemanually or by superimposing digital images. The two images can becompared, for instance, by identifying, from the cancer lesiondistribution image, the organ wherein the main cancer lesion is present,and then determining the location of the identified organ in thenear-infrared fluorescence intensity distribution image. In other words,the area detected in the near-infrared fluorescence intensitydistribution image but not in the cancer lesion distribution image canbe discovered. The data collection method of the present invention isparticularly useful when the accessory cancer lesion is present in anorgan that cannot be detected in the cancer lesion distribution image.However, the method can also be used for detecting a lesion (anaccessory lesion) in parts that cannot be detected in the cancer lesiondistribution image although the organ itself can be detected in thatimage. By using the data collection method of the present invention, acancer lesion (an accessory lesion) with a long axis length of less than5 mm can be detected.

Next, the accessory cancer lesion detector is described. In theabove-described accessory cancer lesion detection method and datacollection method, an accessory cancer lesion detector that comprises atleast an irradiation means and an imaging means can be used fordetecting an accessory cancer lesion during surgery for shrinking,destruction, or resection of a cancer lesion.

FIG. 1 is a configuration diagram of an embodiment of such an accessorycancer lesion detector. FIG. 2 is a perspective view showing theconfiguration of the excitation light source unit and imager used in theaccessory cancer lesion detector shown in FIG. 1.

The accessory cancer lesion detector of the embodiment shown in FIG. 1irradiates the excitation light 10 of a certain wavelength on to thetarget organ 20, and observes the image created by the fluorescence(fluorescence image 11) emitted by the target organ 20, to detect theaccessory cancer lesion. In the detection of an accessory cancer lesionusing this detector, indocyanine green is injected beforehand at a pointnear the lesion in the target organ 20, or intravenously. Then, thenear-infrared fluorescence coming from the indocyanine green accumulatedin the accessory cancer lesion is observed to detect the accessorycancer lesion.

The accessory cancer lesion detector shown in FIG. 1 comprises theexcitation light source unit 2 (irradiation means), optical filter 3,imager 4 (imaging means), controller 5, and image display device 6. Theexcitation light source unit 2 has a plurality of excitation lightsources 2 a, and a support 2 b on one side whereof the excitation lightsources 2 a are installed. Each of the excitation light sources 2 acomprises a light source that radiates light of the same wavelength asthe excitation light, and is used to irradiate the target organ 20 withthe excitation light 10. As shown in FIG. 2, the excitation lightsources 2 a are arranged two-dimensionally with symmetry about thecentral axis Ax of the excitation light source unit 2, which will becomethe optical axis of the detector.

As mentioned earlier, it is preferable to use semiconductor lasers (LD)or light emitting diodes (LED) as the excitation light sources 2 a. Thewavelength of the excitation light 10 supplied by the excitation lightsource 2 a is suitably selected (760 nm for instance) from thenear-infrared wavelength band, as the absorption band of indocyaninegreen is in that range.

An opening 2 c is provided on the support 2 b at its central location,which includes the central axis Ax. The opening 2 c is provided for thepassage of the fluorescence image 11, which comes from the target organ20 towards the front of the excitation light source unit 2, to pass toits rear. The plurality of excitation light sources 2 a described aboveis aligned 2-dimensionally to surround the opening 2 c. In such aconfiguration, it is suitable to set the optical axes of thoseexcitation light sources 2 a located close to the opening 2 c inclinedtowards the central axis Ax to prevent the intensity distribution of theexcitation light 10 irradiated on to the target organ 20 from becomingweak at the center because of the effect of the opening 2 c.

An optical filter 3 is installed in the opening 2 c of the support 2 b.This optical filter 3 allows the passage of light of the wavelength bandof the fluorescence image 11 emitted by the accessory cancer lesions,out of the light coming from the target organ 20, which is the object ofobservation. A filter having transmission characteristics that cut offlight of wavelengths other than that of the fluorescence image 11, whichincludes the excitation light 10 reflected back by the target organ 20,is preferably used as the optical filter 3.

The imager 4 is installed at the rear of the excitation light sourceunit 2. In this embodiment, the imager 4 is integrated with theexcitation light source unit 2, with a common optical axis Ax. Thefluorescence image 11 emitted by the fluorescent dye in an accessorycancer lesion, which is excited by the excitation light 10 irradiated bythe excitation light sources 2 a, passes through the opening 2 c and theoptical filter 3 of the support 2 b, and arrives at the imager 4. Theimager 4 captures the incoming fluorescence image 11 and outputs, asimage data, the observed image thus obtained.

A CCD camera that can capture 2-dimensional images is used, forinstance, as the imager 4. The imager preferably has the capability tocapture, with high sensitivity, the light of the wavelength band of thefluorescence image 11 (the near-infrared wavelength band, as usually thetarget is a fluorescence image of about 800 nm). A power source for theexcitation light sources and a power source for the imager are connectedrespectively as required with the plurality of excitation light sources2 a and the imager 4. The power sources, etc are not shown in FIG. 1.These devices can also be battery-driven.

A controller 5 is provided for the observed image output from the imager4. The controller 5 is a means of manually or automatically controllingthe image data of the observed image output by the imager 4. Thecontroller 5 in this embodiment has a brightness control 5 b andcontrast control 5 c, which respectively control the brightness andcontrast of the observed image output by the imager 4. The controlsettings of the observed image, in the controls 5 b and 5 c, are inputfrom the control panel 5 a. The control panel 5 a sets the controlsettings of the observed image automatically or through inputs from theviewer. If the control settings are fixed, there is no need to providethe control panel 5 a. The transmission of image data from the imager 4to the controller 5 can be through a cable, or wireless.

An image display device 6 and image recorder 7 are connected to thecontroller 5. The image display device 6 displays, on its displaysection 6 a, the observed image 15 that has been controlled by thecontroller 5, as the image to be used for detecting an accessory cancerlesion. Examples of image display devices 6 include a CRT monitor and aliquid crystal display, attached to a CCD camera used as the imager 4.The image recorder 7 is a means of recording the observed image datacontrolled by the controller 5. Examples of devices that can be used asthe image recorder 7 include a videotape recorder that records theobserved image on videotape, a recording medium.

Now the method of detecting an accessory cancer lesion using theaccessory cancer lesion detector illustrated in FIG. 1 is described.First, the fluorescent dye indocyanine green is injected intravenously.After the lapse of a certain time (typically 1 to 10 days from theintravenous injection), when excitation light 10 of a certain wavelength(760 nm for instance) is irradiated on the target organ 20 from theexcitation light source unit 2, a fluorescence image 11 in thenear-infrared wavelength band is emitted by the accessory cancer lesionbecause of the indocyanine green. Here, the optical filter 3 allows thepassage of the fluorescence image 11 while cutting off the reflectedlight coming from the target organ 20 that is being irradiated by theexcitation light 10.

The fluorescence image 11 that passes through the optical filter 3 iscaptured by the CCD camera used as the imager 4, and the data of theobserved image is output from the CCD camera to the controller 5. Thecontroller 5 controls the brightness and contrast of the observed imagecoming from the imager 4. As a result, the observed image 15 (whichincludes the image of the main cancer lesion) containing the accessorycancer lesion image 16 is generated. When such an image is displayed onthe display section 6 a of the image display device 6, the detection ofthe accessory cancer lesion is realized. Furthermore, if necessary, theobserved image 15 is recorded on a recording medium in the imagerecorder 7.

The accessory cancer lesion area data can be collected by comparing thenear-infrared fluorescence intensity distribution image, obtained asdescribed above, with the cancer lesion distribution image obtained bythe use of x-rays, nuclear magnetic resonance, or ultrasound on thetarget organ 20 before administering the indocyanine green.

EXAMPLES

The present invention will now be described in more specific terms,citing some examples of the present invention. However, these examplesin no way restrict the scope of the invention, and various modificationscan be made within the technical scope of the present invention.

In the examples 1 to 5 given below, the ICG (0.5 mg/kg) was injectedintravenously a few days before the surgery. In other words, in theexamples 1, 2, 3, 4, and 5, the intravenous ICG injection wasadministered, respectively, 4, 4, 8, 1, and 4 days before the surgery.The liver was observed with the infrared camera system PDE (PhotodynamicEye (trade name), Hamamatsu Photonics K.K.) having the configurationshown in FIGS. 1 and 2, used as the accessory cancer lesion detector,and hepatocellular carcinoma was detected. In examples 1 to 4, thecancer was primary liver cancer, and in Example 5 it was metastaticliver cancer.

Example 1

Example 1 was a case of a male in his 50s. Preoperative contrast CTdetected the presence of a single HCC, 40 mm in diameter, in the S5/8segment of the liver. FIG. 3A is an image showing the result of contrastCT. The arrow indicates the HCC. When the patient's abdomen was cut openand intraoperative diagnosis was carried out with the PDE, a fluorescentarea, 5 mm in diameter, was detected in the S4 segment of the liver, inaddition to the main tumor (main lesion). Therefore, this part (theaccessory lesion) was also resected. FIG. 3B is a near-infraredfluorescence intensity distribution image (measured after the abdomenwas opened but before the resection) from ICG in the liver. The arrow(arrowhead) at right indicates the fluorescent area (accessory lesion),5 mm in diameter, in the S4 segment of the liver. The larger fluorescentarea, indicated by the arrow on the left, is the main tumor area (mainlesion). Based on histological tests on the resected tissue, the maintumor was diagnosed as moderately differentiated HCC, and the accessorylesion detected in the S4 segment of the liver was diagnosed as highlydifferentiated HCC. FIG. 3C is a micrograph of a tissue section of theaccessory lesion (fluorescent area, 5 mm in diameter, in the S4 segmentof the liver), and FIG. 3D is a magnified image of the micrograph ofFIG. 3C.

Example 2

Example 2 was a case of a male in his 70s. Preoperative contrast CTdetected the presence of a single HCC, 45 mm in diameter, in the S2/3/4segment of the liver. FIG. 4A is an image showing the result of contrastCT. The arrow indicates the HCC. From the contrast CT image, the HCC wasdiagnosed to be simple nodular type. But after opening of the abdomen,and intraoperative diagnosis using the PDE, some fluorescent areas(accessory lesions), 2 to 3 mm in diameter, were detected scatteredaround the main tumor (main lesion). Therefore, the area to be resectedwas made to include these, and the resection was carried out. FIG. 4B isa near-infrared fluorescence intensity distribution image (measuredafter the abdomen was opened but before the resection) from ICG in theliver. The fluorescent area indicated by the arrow at right is the maintumor area (main lesion). The two arrows (arrowheads) at left indicatefluorescent areas (accessory lesions), 2 to 3 in mm diameter, seenaround the main tumor. Based on histological tests on the resectedtissue, the main tumor was diagnosed to be a moderately differentiatedHCC, and the scattered nodules (accessory lesions) were diagnosed to besatellite nodules of simple nodular HCC with extranodular growth. FIG.4C is a micrograph of a tissue section of an accessory lesion(fluorescent area, 2 to 3 mm in diameter seen around the main tumor),and FIG. 4D is a magnified image of the micrograph of FIG. 4C.

Example 3

Example 3 was a case of a male in his 60s. Preoperative contrast CTdetected the presence of a single HCC, 25 mm in diameter, in the S8segment of the liver. FIG. 5A is an image showing the result of contrastCT. The arrow indicates the HCC. When the abdomen was opened, thesurface of the liver was found to be irregular. Therefore, theidentification of the main tumor (main lesion) by intraoperativeultrasonography diagnosis was difficult. But intraoperative diagnosisusing the PDE could confirm the HCC areas (main and accessory lesions)as fluorescent areas, which made it easy to decide the area to beresected. FIG. 5B and FIG. 5C are near-infrared fluorescence intensitydistribution images (measured after the abdomen was opened but beforethe resection) from ICG in the liver. The arrow in FIG. 5B indicates themain tumor (main lesion), and the arrow (arrowhead) in FIG. 5C indicatesa fluorescent area (accessory lesion), 5 mm in diameter, in the S5segment of the liver. Based on these measurements, the fluorescent area(accessory lesion), 5 mm in diameter, in the S5 segment of the liver wasalso resected in addition to the main tumor (main lesion). Based onhistological tests on the resected tissue, the main tumor (main lesion)was diagnosed to be a highly differentiated HCC, and the accessorylesion in the S5 segment was diagnosed as slightly less differentiatedHCC than the main tumor. FIG. 5D is a micrograph of the accessory lesion(arrowhead).

Example 4

Example 4 was a case of a male in his 70s. Preoperative contrast CTdetected the presence of a single HCC, 25 mm in diameter, in the S5segment of the liver. FIG. 6A is an image showing the result of contrastCT. The arrow indicates the HCC. When the abdomen was opened, thesurface of the liver was found to be irregular, and the identificationof the main tumor by intraoperative ultrasonography diagnosis wasdifficult. But intraoperative diagnosis by the PDE could confirm the HCCareas (main and accessory lesions) as fluorescent areas, which made iteasy to decide the area to be resected. FIG. 6B is a near-infraredfluorescence intensity distribution image (measured after the abdomenwas opened but before the resection) from ICG in the liver. Thefluorescent area indicated by the arrow at left is the main tumor area(main lesion), and the two arrows (arrowheads) on the right indicatefluorescent areas (accessory lesions), 3 mm in diameter, observed aroundthe main tumor. Based on the above measurements, more than onefluorescent area (accessory lesions), each 3 mm in diameter, wereresected in addition to the main tumor (main lesion). Further, theresected liver was fixed in formalin and made into 3 mm thick slices(FIG. 6C and FIG. 6G), and the cross-sections observed with the PDE(FIG. 6D and FIG. 6H). Based on histological test of the partcorresponding FIG. 6C and FIG. 6D, the main tumor and the scatterednodules were diagnosed as highly differentiated HCC. FIG. 6E is amicrograph of a tissue section of an accessory lesion (fluorescent area,3 mm in diameter), and FIG. 6F is a magnified image of the micrograph ofFIG. 6E. The near-infrared fluorescence intensity distribution image ofthe part corresponding the area shown in FIG. 6G (FIG. 6H) revealedlight emission from areas where no nodule was detected macroscopically(double arrowheads in FIG. 6H). Based on histological test of the areasindicated by the double arrowheads in FIG. 6H, these areas were alsodiagnosed as highly differentiated HCC. FIG. 6I is a micrograph oftissue section showing these parts, and FIG. 6J is a magnified image ofthe micrograph of FIG. 6I.

Example 5

Example 5 was a case of a male in his 50s. Preoperative contrast CTdetected the presence of a liver tumor, 25 mm in diameter, in the S2segment and a liver tumor, 22 mm in diameter, in the S7 segment of theliver. FIG. 7A is an image showing the result of contrast CT. The arrowindicate liver tumor. When the abdomen was opened, and the PDE was usedintraoperatively, apart from the two lesions identified before thesurgery, a fluorescent area (accessory lesion), 5 mm in diameter, wasalso detected in the S4 segment of the liver, which was difficult toidentify definitely by palpation or intraoperative ultrasonography.Therefore, all these areas were included in the area to be resected, andliver resection performed. FIG. 7B is a near-infrared fluorescenceintensity distribution image (measured after the abdomen was opened butbefore the resection) from ICG in the liver. The arrow (arrowhead)indicates a fluorescent area (accessory lesion), 5 mm in diameter.Histological test of the resected tissue confirmed that it hadadenocarcinoma, which was diagnosed as metastasis of colon cancer intothe liver. FIG. 7C is a micrograph of a tissue section of the accessorylesion (fluorescent area, 5 mm in diameter), and FIG. 7D is a magnifiedimage of the micrograph of FIG. 7C.

In all the cases examined, minute HCC or metastatic cancers, which couldnot be confirmed by conventional contrast CT, could be discovered byintraoperative diagnosis with a PDE. Such minute HCC or metastaticcancers were the ones that would have been missed in conventionalhepatectomy. Such missing is believed to be one of the reasons for thepoor 5-year recurrence-free survival.

The ICG infrared camera system described above would be useful not onlyfor intraoperative detection of minute HCC and metastatic cancer butalso for determining the liver resection line, and for modifying thesurgical technique.

1-25. (canceled)
 26. A method for identifying a cancer lesion, themethod comprising: administering indocyanine green to a living body andallowing the indocyanine green to accumulate in the cancer lesion;surgically exposing a target organ suspected of having cancer andirradiating the target organ with excitation light of indocyanine green,and causing the indocyanine green to emit near infrared fluorescenceradiation; imaging the target organ to generate a near infraredfluorescence image; and identifying with the near infrared fluorescenceimage an area having the near-infrared fluorescence radiation as thecancer lesion in the target organ.
 27. The method according to claim 26,wherein the step of imaging the target organ is carried out at least 1day after the administration step.
 28. The method according to claim 26,wherein the cancer lesion is at least one of a main lesion and accessorylesion.
 29. The method according to claim 26, wherein the cancer is asolid cancer or a metastatic cancer.
 30. The method according to claim26, wherein the target organ is at least one of a stomach, an esophagus,a colon and a liver.
 31. The method according to claim 26 furthercomprising the steps of: acquiring a second image by at least one ofX-ray imaging, magnetic resonance imaging, and ultrasonic imaging; andcomparing the second image with the near infrared fluorescence image.